Functional fluid compositions containing tetrahydrofurfuryl meth-acrylate



United States Patent 3 321 405 FUNCTIONAL FLUlD COMPOSITIONS CON-TAINING TETRAHYDROFURFURYL METH- ACRYLATE Edward H. Mottus and Joseph E.Fields, St. Louis, Mo.,

assignors to Monsanto Company, St. Louis, Mo., a corporation of DelawareNo Drawing. Original application Nov. 19, 1962, Ser. No. 238,706.Divided and this application Jan. 21, 1966, Ser. No. 522,025

9 Claims. (Cl. 25251.5)

The invention relates to a new and improved process for providingoil-soluble tetrahydrofurfuryl methacrylate polymers useful as oiladditives and which have improved viscosity-stability in the presence ofheavy duty barium detergent additives. This application is a division ofcopending application Ser. No. 238,706, filed Nov. 19, 1962, (now PatentNo. 3,265,768) which is in turn a continuation-in-part of copendingapplication Ser. No. 224,883, filed Aug. 31, 1962. These additives areespecially useful as low-temperature detergency additives in mineraloils.

It is an object of the invention to provide a new and improved method ofmaking the new tetrahydrofurfuryl methacrylate polymers.

It is another object of this invention to provide new and usefullow-temperature detergency additives for oils and to oil compositionsthereof.

These and other objects of the invention will become apparent as thedetailed description of the invention proceeds.

In the new process of the invention the alkyl methacrylate monomers arepolymerized for a sufficient length of time prior to the addition of thetetrahydrofurfuryl methacrylate monomer that the final product is stablein the presence of heavy-duty detergents such as barium detergents. Thetime for polymerizing the alkyl methacrylate monomers before adding thetetrahydrofurfuryl methacrylate monomer will vary somewhat depending onthe particular alkyl methacrylate monomers being used and the amount andmethod of addition of the tetrahydrofurfuryl methacrylate monomer;however, normally the alkyl methacrylate monomers are polymerized toincorporate not more than about 90 mole percent of the alkylmethacrylate monomers in the polymer before adding thetetrahydrofurfuryl methacrylate monomer, and usually from about 40 toabout 75 mole percent of the alkyl methacrylates will be incorporatedinto the polymer before the addition of the tetrahydrofurfurylmethacrylate monomer; then, the polymerization is continued tocompletion causing substantially all of the monomers to be incorporatedinto the polymer. A freeradical type catalyst is used as is customarilyused for alkyl methacrylate polymerization, and reaction conditions oftemperature and pressure are those customarily used. The monomerS-methyl tetrahydrofurfuryl methacrylate can be used instead oftetrahydrofurfuryl methacrylate or mixtures thereof can be used.

The polymer additives made by the new process of the invention are thetetrahydrofurfuryl methacrylate and alkyl methacrylate polymerscontaining a minor amount of tetrahydrofurfuryl methacrylate and inmajor amount alkyl methacrylates. The major amount means in excess of 50percent by weight and a minor amount means less than 50 percent byWeight, and obviously when two minor amounts are specified along withthe major amount 3,321,405 Patented May 23, 1957 the two minor amountsmust add up to less than 50% by weight.

As dispersant additives these tetrahydrofurfuryl methacrylate/alkylmethacrylate polymers of the invention are useful as additives to oils,such as automatic transmission oils, lubricating oils, diesel oils,furnace oils, hydraulic oils and the like. The oils can either bemineral or synthetic oils. Normally these polymers as dispersantadditives will be incorporated in oil in amounts of from about 0.5 toabout 15% based on the oil and the polymer, preferably from about 1 toabout 10%; except that if made up in concentrate form for blending back,they may be incorporated in amounts of about 15 to 60%, preferably tothe extent of at least about 1% in oil. The solubility will, of course,vary depending on the particular oil used. Oil solubility can beregulated to a certain extent by limiting the molecular weight of thepolymer, specific viscosity measurements being indicative of molecularweight. Specific viscosity, 1% in benzene at 25 C. should be between 0.4and 7.0, preferably between 0.6 and 3.0. Solubility in oil can also beregulated by the number of carbon atoms in the alkyl groups of themethacrylates, which should be at least 6 carbon atoms, and preferablyaverage at least 7.5 where the oil is a mineral lubricating oil. Singlealkyl methacrylates can be used in making the polymers such as thosehaving from about C to about C alkyl groups or mixtures of methacrylatemonomers such as C C plus C -C alkyl methacrylates. If a mixture ofshort and long-chain alkyl methacrylate monomers are used with thetetrahydrofurfuryl methacrylate to form polymers of the invention, thelong-chain alkyl methacrylates are preferably present in weight percentexcess over the short-chain alkyl methacrylates, but in any event theamount of short-chain alkyl methacrylate is restricted to insure oilsolubility of the polymer. For the purposes of the invention, oilsolubility is defined as the polymer being soluble at 25 C. to theextent of at least 1% in a petroleum base hydraulic fluid meetinggovernment specifications MIL-0-5606.

The following is a non-limiting and illustrative list of alkylmethacrylate monomers from which can be chosen single monomers orcombinations of monomers for use in making the polymers of theinvention: methyl methacrylate, ethyl methacrylate, n-propylmethacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutylmethacrylate, t-butyl methacrylate, n-amyl methacrylate, nhexylmethacrylate, n-heptyl methacrylate, n-octyl methacrylate, isooctylmethacrylate, n-decyl methacrylate, ndodecyl methacrylate, t-dodecylmethacrylate, Oxotridecyl methacrylate, Lorol methacrylate, tallowmethacrylate, n-eicosyl methacrylate, etc. Lorol alcohols are mixturesof straight-chain C -C alcohols being mostly C alcohols. Tallowmethacrylate is a mixture of about 33% by weight of C and 67% weight ofC straight-chain alkyl methacrylates..

In the method of the invention tetrahydrofurfuryl methacrylate and alkylmethacrylates can be polymerized with minor amounts of other monomerssuch as N-vinyl-2-pyrrolidone, vinyl pyridine, vinyl acetate,vinyloxyethanol, methacrylamides, hydroxyalkyl methacrylates andacrylates, e.g. hydroxyethyl methacrylate, aminoalkyl methacrylates andacrylates, e.g. dimethylaminoethyl methacrylate, t-butylaminoethylmethacrylate, etc., polyalkyleneoxy methacrylates and acrylates,polyaminoalkylene acrylates and methacrylates, hydroxyand aminoalkylderivatives of fumaric and maleic acids, etc. These other monomers willbe added with the alkyl methacrylates at the start of thepolymerization, and the tetrahydrofurfuryl methacrylate will be addedlate in the usual fashion of the method of the invention.

Illustrative of other miscellaneous monomers which can be copolymerizedwith a tetrahydrofurfuryl ester are the following: methacrylic acid,acrylic acid, fumaric acid, maleic acid, maleic anhydride, etc. Thesemonomers also will be added with the alkyl methacrylates at the start ofthe polymerization.

The process of the invention is carried out using freeradical generatingcatalysts such as peroxides, hydroperoxides, azo, boron and peroxygencompound catalysts, etc., including irradiation with ultraviolet rays,X-rays, -rays, neutrons and the like. Temperatures of reaction will bethe same as those customarily used for polymerizing with the particularcatalyst used and pressure or vacuum operation can be used as desirable,depending on the temperature of polymerization and solvent used inpolymerization. It will be desirable in most cases to use a solventduring polymerization, such as benzene, toluene, xylenes and the like tomaintain fluidity of the polymerizing mass and to facilitate completionof the polymererization. If the polymer is .to be dissolved in oil, theoil can be added to the reaction mixture before the removal of thebenzene. Rather than using benzene or similar volatile solvents, an oilsuch as a mineral oil can be used as the solvent during polymerization,the polymer product can easily be recovered and purified either bydistillation under reduced pressure or by using a counter-solvent suchas methanol to precipitate the polymer from the benzene. Reprecipitationfrom benzene using methanol can be used to further purify the polymer.

The invention will be more clearly understood from the followingdetailed description of specific examples thereof.

Example 1 The apparatus used for making this run was a 4-necked glassflask fitted with a condenser, a stirrer, a thermometer and a Y-fittingto. take two dropping funnels. In the stirrer motor circuit are ammetersto determine the power requirements. Ammeter readings are observed tofollow the increase in viscosity in the polymerization mixture. Theapparatus is flushed with nitrogen both before and duringpolymerization. To the flask was charged 64.6 g. of tridecylmethacrylate, 46.8 g. of tallow methacrylate, 8.5 g. of methylmethacrylate and 6.2 g. of tetrahydrofurfuryl methacrylate. A sample of25 ml. of the monomer mixture was removed from the flask and to this wasadded 0.25 g. of benzoyl peroxide catalyst. The catalyst was dissolvedin the monomers and added to a dropping funnel. The polymerization wascarried out at about 95 C. At the beginning of the run ml. of themonomer catalyst mixture was added to the flask. Periodically during therun 10' ml. amounts of base oil No. 1 was added to .the reaction mixtureto reduce the viscosity. At the end of one hour of polymerization 3 ml.of catalyst monomer mixture was added to the reaction flask, 3 ml. moreat the end of one and three quarters hours, three ml. more at the end of2V2 hours, 3 ml. more at the end of three hours and a quarter and thebalance of the catalyst monomer mixture was added to the reactionmixture at the end of four hours.

During the polymerization run a total of about ml. of base oil No. 1 wasadded to the reaction mixture in 10 ml. amounts. At the end of thepolymerization run an additional 120 ml. of base oil No. 1 was added tothe reaction mixture. Additional base oil No. 1 was added to thereaction mixture to provide a 37% concentrate of polymer in oil. To theconcentrate was added 1.25 g. of an antioxidant which was4,4-methylene-bis-[2,6-ditert-butylphenol], and the antioxidant wasincorporated into the concentrate by mixing and heating to 1 10 C./ 100mm. A sample of the 37% concentrate was diluted with base oil No. 2 to3% polymer concentration and viscosity determinations were made of the3% poly- 4 mer in oil. Specific viscosity at 100 F. was 0.858 and at 210F. was 1.089. Efliciency was 1.269. Efliciency is a measure of theviscosity-temperature coeflicient of a polymer in the solvent in whichthe measurements are made.

Specific viscosity at 210 F.

specific viscosity at 100 F.

Viscosity at 100 F., SUS 113 Viscosity at 210 F., SUS 40 Flash point, F.380 Specific gravity at 60 F. 0.8639

Base Oil No. 2.This oil is a solvent refined Mid- Continent petroleumlubricating oil, having the following properties:

Viscosity at 210 F., centistokes 10.39 Viscosity at 100 F., centistokes91.73 Viscosity index 103.4

Flash point, Cleveland Open Cup, F

Example 2 This example was carried out in a similar manner to Example 1,except that the tetrahydrofurfuryl methacrylate mono-mer was not addedto the flask as were the other monomers at the beginning of thepolymerization run. After 1% hours of polymerization, one half of thetetrahydrofurfuryl methacrylate monomer was added in base oil No. 1 tothe reaction mixture, and after two and one half hours of polymerizationthe balance of the tetrahydrofurfuryl methacrylate monomer was added inbase oil No. 1 to the polymerization mixture. Viscosity and efliciencydeterminations were made on the product of Example 2 in a similar manneras described for the product of Example 1. In Table 1 which is insertedlater, Examples 1 and 2 and the other experimental examples aresummarized.

Examples 3 and 4 Except for the tetrahydrofurfuryl methacrylate monomerall of the monomers were charged to the flask at the beginning of thepolymerization. In addition to the other monomers of Example 1, a smallamount of hydroxypropylmethacrylate was used. After one andthreequarters hours of polymerization, one half of thetetrahydrofurfuryl methacrylate monomer was added to the polymerizationmixture in base oil No. 1, and after two and a half hours ofpolymerization the balance of the tetrahydrofurfuryl methacrylatemonomer was added to the polymerization mixture in base oil No. 1. Atthe end of the polymerization run suflicient base oil No. 1 was added tomake a 37% concentrate of the polymer. Other for the exceptions notedabove, this run was carried out in a similar manner to Example 1. Thefinal concentrate product was divided into two parts and to one part ofthe concentrate was added an ashless detergent in minor amount, and thissample with the ashless detergent in it was labeled Example No. 4.

Examples 5 and 6 In this example the hydroxypropyl methacrylate ratherthan the tetrahydrofurfuryl methacrylate was added late in thepolymerization reaction. All of the monomers except thehydroxypropylmethacrylate were charged to the polymerization vessel atthe beginning of the polymerization period. After one and three-quartershours of polymerization one half of the hydroxypropyl methacrylatedissolved in base oil No. 1 was added to the polymerization mixture, andafter two and a half hours of polymerization, the balance of thehydroxypropyl methacrylate was added to the polymerization mixture. Atthe end of the polymerization a 37% concentrate was made by addingadditional base oil No. 1. Other than the exceptions noted above,Example 5 was conducted in the usual fashion of Example 1. Theconcentrate was divided in two portions and to one portion was added aminor amount of the antioxidant 4,4'-methylene-bis-[2,6-di-tertbutylphenol]. The antioxidant was incorporated into the concentrate inthe usual fashion, and the sample with the antioxidant in it was labeledExample No. 6.

Examples 7 and 8 This example was a run wherein all of the monomersexcept the tetrahydrofurfuryl methacrylate and methyl methacrylate werecharged to the reaction flask at the beginning of the polymerizationrun. One-half of the tetrahydrofurfuryl methacrylate monomer andone-half of the methyl methacrylate monomer were added to thepolymerization mixture in base oil No. 1 after one hour ofpolymerization time, and the other half of these two monomers was addedto the polymerization mixture after one and three-quarters hours ofpolymerization time. Other than this Example 7 was carried out in theusual batch fashion. At the end of the polymerization run a 37%concentrate was made of the product by adding additional base oil No. 1.The concentrate product was divided in two parts and to one part wasadded a minor amount of ashless detergent, and the portion containingthe ashless detergent was designated Example No. 8.

Examples 9 and 10 This example was a typical polymerization run whereinall of the monomers were charged to the reaction flask at the beginningof the polymerization run with the exception of methyl methacrylate andhydroxypropyl metl1acry late. The methyl methacrylate and hydroxypropylmethacrylate monomers were dissolved in base oil No. 1 and onehalf ofeach of these monomers was added to the polymerization reaction at theend of one hour of polymerization and the other half at the end of oneand threequarters hours of polymerization. At the end of thepolymerization run the 37% concentrate of the additive was made byadding base oil No. l. The concentrate was divided into two portions andto one portion was added a minor amount of ashless detergent, and thisportion containing the ashless detergent was labeled Example No. 10.

Examples 11 and 12 In this example all of the monomers were added to thepolymerization flask at the beginning of the polymerization run exceptthe tetrahydrofurfuryl methacrylate monomer. At the end of one hourpolymerization onehalf of the tetrahydrofurfuryl methacrylate monomerwas added to the polymerization reaction dissolved in base oil No. 1,and at the end of one and three-quarters hours the balance of thetetrahydrofurfuryl methacrylate monomer was added to the polymerizationmixture. In the usual fashion a 37% concentrate of the polymer was madeup. To one-half of this sample of concentrate was added a minor amountof ashless detergent, and this sample was labeled Example No. 12.

6 Examples 13 and 14 In this example all of the monomers were added tothe polymerization flask at the beginning of the polymerization reactionexcept the tetrahydrofurfuryl methacrylate monomer. At the end of oneand one-half hours of polymerization, one-half of the tetrahydrofurfurylmethacrylate monomer dissolved in base oil No. 1 was added to thepolymerization reaction, and at the end of two and one-quarter hours thebalance of the tetrahydrofurhiryl methacrylate monomer was added. Theusual 37% concentrate was made. To one-half of the concentrate was addeda minor amount, 5.7 g. of ashless detergent and this was labeled ExampleNo. 14.

Examples 15 and 16 This example was a modified batch-type run in whichone-half of all of the monomers plus all of the hydroxypropylmethacrylate monomer was added to the flask at the beginning of thepolymerization run, and the other half of the monomers plus all of thetetrahydrofurfuryl methacrylate monomer was added to a dropping funnel.At the end of one and one-half hours of polymerization one-third of themixture of monomers was added from the dropping funnel, at the end oftwo hours of polymerization one-third more of the monomers was added andat the end of two and one-half hours the balance of the monomers fromthe dropping tunnel was added to the polymerization mixture. At the endof the polymerization run the 37% concentrate was made in the usualfashion, and to one-half of the 37% concentrate was added 5.3 g. ofashless detergent which was stirred in at C. The sample containing theashless detergent was labeled Example No. 16.

Examples 17 and 18 In this example all of the monomers were charge-d tothe reaction flask at the beginning of the polymerization run except thetetrahydrofurfuryl methacrylate monomer. At the end of one andthree-quarters hours of polymerization one-half of thetetrahydrofurfuryl methacrylate monomer was added to the polymerizationmixture dissolved in base oil No. 1, and at the end of two and onehalfhours of polymerization the other half of the tetrahydrofurfurylmethacrylate monomer was added to the polymerization mixture. The usual37% concentrate was made in base oil No. 1. To one-half of theconcentrate was added 5.0 g. of ashless detergent which was stirred inat 100 C., and this was labeled Example No. 18.

Examples 19 and 20 This example was run in a manner similar to Example15 in that one-half of all monomers except the hydroxypropylmethacrylate monomer and all of the tetrahydrofurfuryl methacrylatemonomer was added late in the polymerization run from a dropping funnel.The other half of the monomers, including all of the hydroxypropylmethacrylate monomer and none of the tetrahydrofurfuryl methacrylatemonomer was added to the polymerization flask at the beginning of therun. At the end of one and one-half hours of polymerization one-third ofthe monomers were added to the reaction mixture from the droppingfunnel, at the end of two hours of polymerization one-third more of themonomers were added to the polymerization reaction from the droppingfunnel and at the end of two and one-half hours the balance of themonomers were added from the dropping funnel to the reaction flask. Theusual 37% concentrate was made. To onehalf of this concentrate was added5.4 g. of ashless detergent, and this was labeled Example No. 20.

In Table 1, which follows, are summarized 2O experimental examples.

TABLE 1 Specific Viscosity, Process Details Ex. at- Time, No. MonomersMonogegs, Mole Elliciency Hrs.

100 F. 210 F. Temp, C. Solvent Catalyst 1 TrM/TaM/lTM/THFM48.2/27.6/16.9/7.3 0.858 1.089 1.269 6 95 B359 011 #1 BZ202 2---TrM/TaM/MM/THFM 4s.2 27.e/1s.9 7.3 0.968 1.119 1.156 6 95 10 B2202 i-}TrM/TaM/MM/THFM/HPM 4e4/2a5 1a3 a9 a9 1-294 95 B120 2:}TrM/TaM/Ml\i/THFM/HPM 46.4/26.5l16.3/6.9/3.9 1-038 1-347 1-298 6 95B220 5; }TrM/TaM/MM/THFM/HPM- 46.4/26.5/l6.3/6.9/3.9 6% 95 BZZO? g:}TrM/TaM/MM/THFM/HPM 4e4/2a5/1a3/a9/a9 1 8g? 6% 95 BZZO? g: }'r1-M TaMMM THFM HEM-.. 4e4/2a5 1e3/a9 a9 7 95 B110 12" }TrM/TaM/MM/THFM/HPM-43.3/24.s/15.3/13.1/3.e 33g? 7 95 B2202 12: }TrM/TaM/MM/THFM/HPM- 4e42a5 1a3 a9/a9 8' 1: e 95 B120 }TrM/TaM/MM/THFM/HIM 44.0 25.2 20.0 s.93.9 8 2, 3 s 95 B220 gI }TrM/TaM/MM/THFM/HPM 45.6/261/161/102/20 8 6% 95B1202 TrM Tridecyl methacrylate. TaM=Tallow methacrylate.

MM Methyl meth acrylate. THEM Tetrahydrofurturyl methacrylate.

To portions of a number of additive concentrates of 30 the inventionwere added minor amounts of a heavy-duty barium detergent comprisingsulfurized alkylated phenols reacted with barium and carbonated. Table 2below summarizes the effect of varying the time of addition of certainmonomers in producing polymer additives of the invention. Additiveswhich are more viscosity stable in the presence of barium heavy dutydetergents are produced in certain instances.

TABLE 2 Gelled at 3 min.

An examination of the data in Table 2 indicates that thetetrahydrofurfuryl methacrylate monomer should not be added with theother monomers at the beginning of the run, but rather this particularmonomer should not be added until a substantial amount of polymerizationof the other monomers has taken place in order to make a polymer havingimproved stability in the presence of a heavy duty barium detergent.Thus in runs 1, 5, 6, 9 and where the tetrahydrofurfuryl methacrylatemonomer was added with the other monomers at the start in thepolymerization, gels were formed when heavy duty barium detergent wasadded to the concentrates containing the polymer, and of course this isvery undesirable for lubricating oil additive use. In the other runs2-4, 7 and 8 where the tetrahydrofurfuryl monomer was added late in thepolymerization, gels were not formed. It seemed from the results ofTable 2 that the procedure of Example 7 is not as desirable as that ofExamples 2 and 3; however, the product of Example 7 was considerablymore stable in the presence of the barium detergent than the exampleswhere the tetrahydrofurfuryl methacrylate was added at the beginning ofthe polymerization run.

H E M Hydroxyethyl meth acrylate. H P M Hy droxypropyl methacrylate. BZzOz= B enzoyl peroxide.

Although the invention has been described in terms of specifiedembodiments which are set forth in considerable detail, it should beunderstood that this is by way of illustration only and that theinvention is not necessarily limited thereto since alternativeembodiments and operating techniques will become apparent to thoseskilled in the art in View of the disclosure. Accordingly, modificationsare contemplated which can be made without departing from the spirit ofthe described invention.

Having thus described our invention, what we desire to claim and secureby Letters Patent is:

1. A composition having good high temperature and dispersantcharacteristics comprising in major amount a mineral oil and a minoramount of an oil-soluble tetrahydrofurfuryl methacrylate and alkylmethacrylate copolymer mixture having viscosity index improvingproperties, dispersant characteristics and stability in the pres ence ofa barium detergent wherein said copolymer is made by the process ofheating at polymerizing temperatures in the presence of a free radicalcatalyst a major amount of an alkyl methacrylate monomer having not lessthan 6 and not more than carbon atoms in the alkyl group for a timesufiicient to polymerize at least a portion of said alkyl methacrylateto provide said stability, and then adding to the polymerizing alkylmethacrylate under polymerizing conditions a minor amount oftetrahydrofurfuryl methacrylate monomer based on said alkyl methacrylatein a manner to produce a mixture of copolymer species and continuing thepolymerization until substantially all of the monomer content isincorporated in the polymer.

2. A composition of claim 1 wherein said mineral oil contains a basicdetergent additive.

3. A composition of claim 1 wherein from about to about mole percent ofsaid alkyl methacrylate has been incorporated into said copolymermixture before the incorporation of said tetrahydrofurfuryl methacrylatemonomer.

4. A composition of claim 1 wherein the copolymer mixture has a minoramount of vinyloxyethanol.

5. A composition of claim 1 wherein the copolymer mixture has a minoramount of N-vinyl-2-pyrrolidone.

6. A composition of claim 1 wherein the copolymer mixture has a minoramount oft-butylaminoethyl methacrylate.

7. A composition of claim 1 wherein the copolymer mixture has a minoramount of hydroxyethyl methacrylate.

8. A composition of claim 1 wherein the copolymer mixture has a minoramount of hydroxypropyl methacrylate.

9. A composition of claim 1 wherein said alkyl methac-rylate is amixture of alkyl methacrylates having not less than 6 and not more than20 carbon atoms in the alkyl groups, and mixed therewith is a minoramount of C C alkyl methacrylate.

References Cited by the Examiner UNITED STATES PATENTS DANIEL E. WYMAN,Primary Examiner. W. H. CANNON, Assistant Examiner.

1. A COMPOSITION HAVING GOOD HIGH TEMPERATURE AND DISPERSANTCHARACTERISTICS COMPRISING IN MAJOR AMOUNT A MINERAL OIL AND A MINORAMOUNT OF AN OIL-SOLUBLE TETRAHYDROFURFURYL METHACRYLATE AND ALKYLMETHACRYLATE COPOLYMER MIXTURE HAVING VISCOSITY INDEX IMPROVINGPROPERTIES, DISPERSANT CHARACTERISTICS AND STABILITY IN THE PRESENCE OFA BARIUM DETERGENT WHEREIN SAID COPOLYMER IS MADE BY THE PROCESS OFHEATING AT POLYMERIZING TEMPERATURES IN THE PRESENCE OF A FREE RADICALCATALYST A MAJOR AMOUNT OF AN ALKYL METHACRYLATE MONOMER HAVING NOT LESSTHAN 6 AND NOT MORE THAN 20 CARBON ATOMS IN THE ALKYL GROUP FOR A TIMESUFFICIENT TO POLYMERIZE AT LEAST A PORTION OF SAID ALKYL METHACRYLATETO PROVIDE SAID STABILITY, AND THEN ADDING TO THE POLYMERIZING ALKYLMETHACRYLATE UNDER POLYMERIZING CONDITIONS A MINOR AMOUNT OFTETAHYDROFURFURYL METHACRYLATE MONOMER BASED ON SAID ALKYL METHACRYLATEIN A MANNER TO PRODUCE A MIXTURE OF COPOLYMER SPECIES AND CONTINUING THEPOLYMERIZATION UNTIL SUBSTANTIALLY ALL OF THE MONOMER CONTENT ISINCORPORATED IN THE POLYMER.
 6. A COMPOSITION OF CLAIM 1 WHEREIN THECOPOLYMER MIXTURE HAS A MINOR AMOUNT OF T-BUTYLAMINOETHYL METHACRYLATE.